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ANNUAL SUMMARY OF OUTBREAKS IN NEW ZEALAND 2016

PREPARED FOR: Ministry of Health

CLIENT REPORT No: FW17038

PREPARED BY: Health Intelligence Team, Health Group

PUBLISHED: 29 March 2018

This report is available at www.surv.esr.cri.nz

Published: 29 March 2018

Suggested citation:

Institute of Environmental Science and Research Ltd (ESR). Annual Summary of Outbreaks in New Zealand 2016. ESR; 2018.

ISSN: 1176-3485

Client Report FW17038

Reproduction is authorised provided the source is acknowledged.

Annual summary of outbreaks in New Zealand 2016 INSTITUTE OF ENVIRONMENTAL SCIENCE AND RESEARCH LIMITED Page i

ACKNOWLEDGEMENTS

This report was prepared by the Health Intelligence Team of the Institute of Environmental Science and Research Ltd as part of a Ministry of Health contract for scientific services. The production of this report was led by Shevaun Paine.

This report could not have been produced without the continued support of staff in the public health services who provide data from their regions.

Thanks to the following people for their contributions to this report:

Joanne Hewitt for the norovirus section;

Claire Newbern for producing the map;

Liza Lopez for peer checking;

Terry Quirke for peer review;

Tammy Hambling for editing.

DISCLAIMER

This report or document (“the Report”) is given by the Institute of Environmental Science and Research Limited (“ESR”) solely for the benefit of the Ministry of Health, Public Health Services Providers and other Third Party Beneficiaries as defined in the Contract between ESR and the Ministry of Health, and is strictly subject to the conditions laid out in that Contract.

Neither ESR nor any of its employees makes any warranty, express or implied, or assumes any legal liability or responsibility for use of the Report or its contents by any other person or organisation.

Annual summary of outbreaks in New Zealand 2016 Page ii INSTITUTE OF ENVIRONMENTAL SCIENCE AND RESEARCH LIMITED

CONTENTS

Summary .............................................................................................................................. 1

Introduction ........................................................................................................................... 3

Methods ................................................................................................................................ 5

Outbreak definition ........................................................................................................... 5

Data sources .................................................................................................................... 5

Data analysis .................................................................................................................... 6

Data limitations ................................................................................................................. 6

Results .................................................................................................................................. 7

Characteristics of outbreaks ............................................................................................. 7

Distribution of outbreaks by public health unit ................................................................... 7

Multi-regional gastrointestinal outbreaks and other outbreaks of national significance ...... 8

Causal agents .................................................................................................................. 9

Norovirus outbreaks – genotypes and outbreak setting .................................................. 11

Hospitalisations and deaths ............................................................................................ 13

Outbreak settings ........................................................................................................... 15

Modes of transmission .................................................................................................... 16

Foodborne outbreaks ..................................................................................................... 17

Person-to-person outbreaks ........................................................................................... 19

Waterborne outbreaks .................................................................................................... 20

Environmental outbreaks ................................................................................................ 21

Zoonotic outbreaks ......................................................................................................... 22

Time trends 2006–2016 .................................................................................................. 23

Glossary.............................................................................................................................. 27

References ......................................................................................................................... 29

Appendix ............................................................................................................................. 31

Outbreak Report Form .................................................................................................... 31

Annual summary of outbreaks in New Zealand 2016 INSTITUTE OF ENVIRONMENTAL SCIENCE AND RESEARCH LIMITED Page iii

LIST OF FIGURES

Figure 1. Number of outbreaks per 100,000 population by PHU, 2016 .................................. 8

Figure 2. NRL-confirmed norovirus outbreaks by month and genotype, 2016 ..................... 11

Figure 3. NRL-confirmed norovirus outbreaks by setting and genotype, 2016 ..................... 12

Figure 4. Outbreaks and associated cases per 100,000 by year, 2006–2016 ..................... 23

Figure 5. Percentage of outbreaks by pathogen or condition and year, 2006–2016 ............ 24

LIST OF TABLES

Table 1. Number and rate of outbreaks and associated cases by PHU Office, 2016 ............. 7

Table 2. Outbreaks and associated cases by pathogen, 2016 ............................................ 10

Table 3. Hospitalised outbreak cases and total outbreak cases by pathogen or condition, 2016 ........................................................................................................................................... 14

Table 4. Outbreaks and associated cases by setting of exposure/transmission, 2016......... 15

Table 5. Outbreaks and associated cases by mode of transmission, 2016 .......................... 16

Table 6. Foodborne outbreaks and associated cases by pathogen or condition, 2016 ........ 17

Table 7. Foodborne outbreaks and associated cases by setting of food preparation, 2016 . 18

Table 8. Person-to-person outbreaks and associated cases by pathogen or condition, 2016 .................................................................................................................................... 19

Table 9. Waterborne outbreaks and associated cases by pathogen, 2016 .......................... 20

Table 10. Environmental outbreaks and associated cases by pathogen or condition, 2016 21

Table 11. Zoonotic outbreaks and associated cases by pathogen or condition, 2016 ......... 22

Annual summary of outbreaks in New Zealand 2016 Page iv INSTITUTE OF ENVIRONMENTAL SCIENCE AND RESEARCH LIMITED

ABBREVIATIONS

Abbreviation Description

DHB District health board

ESR Institute of Environmental Science & Research Ltd.

FBVE Foodborne Viruses in Europe

NRL Norovirus Reference Laboratory

PHU Public Health Unit

RSV Respiratory syncytial virus

VTEC/STEC Verocytotoxin- or Shiga toxin-producing Escherichia coli

Annual summary of outbreaks in New Zealand 2016 INSTITUTE OF ENVIRONMENTAL SCIENCE AND RESEARCH LIMITED Page 1

SUMMARY

This report summarises data on outbreaks that were reported to the Institute of Environmental Science and Research Limited (ESR) during 2016.

Key findings were:

Outbreaks and associated case rates increased slightly in 2016

There was a non-significant increase in reported outbreaks (▲8.5%, 610 outbreaks) and a significant increase in the number of cases associated with outbreaks (▲22.8%, 11,030 cases) compared with 2015 (559 outbreaks involving 8514 cases). A total of 194 (2.6%) outbreak-associated cases were hospitalised (161 in 2015, 3.3%) and 10 cases died (19 cases in 2015).

The number of outbreaks per 100,000 population increased to 13.0 outbreaks per 100,000 population from 12.1 in 2015, but was the second lowest rate reported since 2008 (10.5 outbreaks). Otago and Wellington reported the highest number of outbreaks per 100,000 population (22.2 and 20.2 respectively), more than one and a half times the national rate.

The national outbreak-associated cases rate was higher in 2016 (235.1 per 100,000 population) than 2015 (185.3) but remained lower than the rate reported in 2009 (250.4), 2012 (237.4) and 2014 (328.7).

Enteric agents most common cause of outbreaks

As in previous years, enteric agents were implicated as the cause in the vast majority of outbreaks, accounting for 91.8% of outbreaks, with the most common causes reported as norovirus (30.3%), Giardia (7.4%) and Cryptosporidium (5.4%). Over half of the cases associated with outbreaks were caused by norovirus (50.3%), whereas the proportions caused by the next two most common enteric pathogens identified were much lower, Campylobacter spp. (9.1%) and sapovirus (6.1%).

The most commonly reported non-enteric agents were influenza and influenza-like illness which accounted for 3.3% of outbreaks, 10.1% of associated cases and three deaths, followed by Bordetella pertussis which accounted for 2.8% of outbreaks

Hospitalisations and deaths

In 2016 there were 53 outbreaks where cases were hospitalised. A total of 194 hospitalisations were reported among 1870 cases. The largest number of hospitalisations was due to Campylobacter spp (41 hospitalisations, 4.2% of cases). The pathogens or conditions with the highest proportion of hospitalised cases were ciguatera fish poisoning (100.0%, 4/4 cases) and Neisseria meningitidis serogroup B (100.0%, 2/2 cases), followed by dengue fever (50.0%, 6/12 cases).

Ten deaths were associated with eight different outbreaks in 2016. The deaths were associated with Campylobacter spp. (3), norovirus (2), VTEC/STEC infection (1), influenza A (1) and parainfluenza (1)*. A pathogen was not identified in three deaths (gastroenteritis (2), acute respiratory infection (1)).

* Both norovirus and influenza A were identified in one outbreak involving one death

Annual summary of outbreaks in New Zealand 2016 Page 2 INSTITUTE OF ENVIRONMENTAL SCIENCE AND RESEARCH LIMITED

Largest outbreak of campylobacteriosis recorded in EpiSurv

In 2016, a nationally significant localised outbreak of Campylobacter was reported. A large multi-agency investigation led by Hawke’s Bay DHB was conducted to investigate a waterborne outbreak of Campylobacter involving 964 notified cases and three deaths. It is estimated that 5500 of Havelock North’s 14,000 residents became ill with campylobacteriosis after consuming contaminated drinking water from the town supply. This was the largest outbreak recorded in EpiSurv since recording began in 1997.

Long-term care facilities the most common outbreak setting

Long-term care facilities (33.3%), childcare centres (18.0%) and private homes (16.4%) continued to be the most common settings for outbreaks. The highest number of cases associated with outbreaks were reported from long-term care facilities (39.8%), childcare centres (19.0%) and schools (12.4%).

Person-to-person the most common mode of transmission

In 2016, 82.3% of outbreaks recorded person-to-person as a mode of transmission, the majority of these as the primary mode, followed by foodborne (15.6%) and environmental (11.1%) transmission. Multiple modes of transmission were implicated in 16.1% of outbreaks.

Norovirus and salmonella the most implicated pathogens in foodborne outbreaks

Norovirus (18.9%), Salmonella (12.6%) and Campylobacter (8.4%) were the pathogens most commonly associated with foodborne outbreaks in 2016. Since 2008, norovirus and Campylobacter have been the most implicated pathogens in foodborne outbreaks.

Trends remain the same as previous years

The 2016 outbreaks showed continuing trends:

1. an increase in outbreaks in institutional settings and decrease in outbreaks linked to

commercial food operators

The proportion of outbreaks set in childcare centres and schools increased in 2016 compared with 2007–2015. Almost two-thirds of outbreaks (65.1%) in 2016 were in institutions, an increase from previous years. Since 2007, institutional outbreaks have accounted for around half of the outbreaks reported each year. Commercial food operators and private homes were the most commonly reported settings prior to 2007.

2. an increase in outbreaks associated with person-to-person transmission.

Over the 2007–2016 period an increase in outbreaks involving person-to-person transmission has been reported. This increases could be partly explained by:

increasing numbers of people living in long-term care facilities due to the ageing population, and increasing numbers of children attending early childhood education facilities due to the funded 20 hours of early childcare introduced in 2007; and

the introduction of national guidelines for the management of norovirus outbreaks in hospitals and elderly care institutions [1] in early 2009, which may have led to increased reporting of outbreaks.

Foodborne transmission was the most commonly reported mode of transmission prior to 2007.


INTRODUCTION

This report summarises data on outbreaks that were reported to the Institute of Environmental Science and Research Limited (ESR) during 2016.

Outbreak surveillance in New Zealand has been conducted by ESR on behalf of the Ministry of Health since 1996. The outbreak surveillance system collects data on disease outbreaks reported by public health units (PHUs). Since 1997, the outbreak surveillance system has been incorporated as a module within EpiSurv, the national notifiable disease database.

Investigating outbreaks provides information to [2]:

halt an outbreak and prevent further illness;

prevent further outbreaks from the immediate source;

prevent further outbreaks from other similar sources;

address public concerns;

involve the public in disease control;

reduce direct and indirect costs;

identify new mechanisms of transmission of known illnesses;

identify new or emerging disease agents;

satisfy legal and international obligations;

improve investigation methods; and

improve public health training.



METHODS

OUTBREAK DEFINITION

The Guidelines for the Investigation and Control of Disease Outbreaks [2] state that the following types of outbreaks should be reported:

two or more cases linked to a common source, in particular where the common source is exposure at a common event, food or water dispersed in the community, an environmental source, or a source in an institutional setting;

a community-wide or person-to-person outbreak (except when the source has become well-established as a national epidemic and reporting it as a discrete event no longer serves a useful purpose);

any other situation where outbreak investigation or control measures are being used or considered. This situation would include a single detected case of an illness that is exotic to New Zealand or has been eradicated (eg, a locally acquired case of dengue fever, poliomyelitis).

Outbreak reporting is encouraged for:

a secondary case in an institution;

household outbreaks—if there is a reasonable possibility that the outbreak resulted from a common source exposure for that household group.

Outbreak reporting is not usually required for:

most secondary cases— with a few exceptions to this (eg measles, pertussis), and where person-to-person spread of a foodborne illness originating from a common source has occurred; Secondary cases should be identified on the outbreak report form.

single cases where a specific contaminated source is identified.

DATA SOURCES

Outbreaks are reported to, or identified by, local PHUs. Each PHU records data on each outbreak on a standardised outbreak report form within EpiSurv. PHUs are encouraged to enter data initially as an interim report that can be finalised when further data becomes available. Data is collated and analysed by ESR on behalf of the Ministry of Health. National data is supplemented by data from ESR’s Enteric Reference Laboratory, and Virology and Public Health Laboratories. If an outbreak is first identified by these laboratories, the appropriate PHU is asked to complete an outbreak report form.

The outbreak report form has the following sections:

reporting authority (outbreak report date and interim or final report);

condition and implicated pathogen, toxin or chemical (name of implicated agent and case definitions);

outbreak demographics (number of cases, outbreak dates, age/sex of cases, incubation period and duration of illness);


circumstances of exposure/transmission (means of outbreak recognition, setting, geographic location, mode of transmission and vehicle/source evidence);

factors contributing to the outbreak (specific factors relating to foodborne, waterborne, person-to-person contact and environmental outbreaks);

management of the outbreak (control measures undertaken).

The terms used in the outbreak report form are defined in a glossary at the end of this report. The form can be found at: http://www.surv.esr.cri.nz/episurv/index.php and in the appendix of this report.

DATA ANALYSIS

This report contains an analysis of outbreak data reported between 1 January and 31 December 2016, and recorded on the EpiSurv database as at 7 April 2017. Any amendments made to outbreak data after 7 April 2017 are not reflected in this report. Outbreaks reported at the end of the period may not have been finalised by the cut-off date. This means that the number of cases reported here may differ from that reported in the Notifiable Diseases in New Zealand Annual Report 2016 [3].

Rates were calculated using national and PHU population figures based on Statistics New Zealand mid-year population estimates for 2016. Tests for statistical significance were calculated using the two-tailed test for difference in proportions (Fisher’s exact).

DATA LIMITATIONS

The available outbreak data is restricted to outbreaks recorded in EpiSurv. Outbreaks are more likely to be reported if they involve unusual pathogens, notifiable diseases, a large number of cases or a well-defined setting. The differing availability of resources among PHUs may also impact on outbreak investigation and reporting at a regional level. Many reported outbreaks remain in the suspected category, as no confirmatory evidence has been found. For these reasons, caution is advised when interpreting the information contained in this report.

This report does not include details about outbreaks of lead absorption (4 outbreaks) reported into EpiSurv in 2016. Responsibility for the collection and reporting of lead absorption, chemical poisoning from the environment and hazardous substance notifications transferred from ESR to the Centre for Public Health Research, Massey University, in January 2013.


RESULTS

CHARACTERISTICS OF OUTBREAKS

There were 610 reported outbreaks (13.0 outbreaks per 100,000 population) in 2016, an increase from the 563 (12.3 outbreaks per 100,000 population) reported in 2015. All but one of the outbreaks were recorded as final reports. A total of 11,030 cases were associated with outbreaks; 33.5% (3696/11,030) of the cases were either clinically or laboratory confirmed and 66.5% (7334/11,030) were classified as probable cases. In 2016, the national rate was 235.1 outbreak-associated cases per 100,000 population, higher than the rate in 2015 (185.5 cases per 100,000 population).

DISTRIBUTION OF OUTBREAKS BY PUBLIC HEALTH UNIT

In 2016, Auckland PHU (29.0%, 162/610) had the highest proportion of outbreaks reported followed by Wellington PHU (17.9%, 100/610). Wellington PHU also reported the highest proportion of outbreak-associated cases (21.7%, 1843/11,030) followed by Canterbury (19.2%, 1638/11,030) (Table 1). Otago PHU reported the highest outbreak rate (22.2 per 100,000 population) and West Coast reported the highest outbreak-associated case rate (2329.2 per 100,000 population) (Table 1, Figure 1).

Table 1. Number and rate of outbreaks and associated cases by PHU Office, 2016

PHU Office

Outbreaks Cases

Total % of

outbreaks (n=610)

Outbreak rate1

Total % of

cases (n=11,030)

Case rate1

Northland 13 2.3 7.6 274 3.2 159.9 Auckland2 162 29.0 9.9 1626 19.1 99.6 Waikato 52 9.3 13.0 937 11.0 234.5 Bay of Plenty 26 4.7 11.5 292 3.4 128.8 Rotorua 19 3.4 17.8 220 2.6 206.4 Taranaki 15 2.7 12.8 224 2.6 191.8 Hawke’s Bay 28 5.0 17.3 1443 17.0 894.1 Gisborne 6 1.1 12.6 135 1.6 282.4 Whanganui 6 1.1 9.5 102 1.2 161.9 Manawatu 21 3.8 12.1 321 3.8 184.3 Wellington3 100 17.9 20.2 1843 21.7 371.5

Nelson Marlborough4 18 3.2 12.3 483 5.7 329.9

West Coast 6 1.1 18.5 757 8.9 2329.2 Canterbury 70 12.5 13.0 1638 19.2 303.6 South Canterbury 6 1.1 10.1 64 0.8 108.1 Otago 49 8.8 22.2 565 6.6 255.7 Southland 13 2.3 13.3 106 1.2 108.1 Total 610 100 13.0 11,030 100 235.1

1 Crude rate of outbreaks per 100,000 population is calculated using Statistics New Zealand population estimates for 2016. 2 Auckland PHU covers the Tāmaki Makaurau-Auckland health district. 3 Includes Wellington, Hutt and Wairarapa health districts. 4 Includes both Nelson and Blenheim offices.


Figure 1. Number of outbreaks per 100,000 population by PHU, 2016

MULTI-REGIONAL GASTROINTESTINAL OUTBREAKS AND OTHER OUTBREAKS OF NATIONAL SIGNIFICANCE

Monitoring of gastrointestinal outbreaks is undertaken at a national and local level. Where a multi-regional outbreak is suspected, ESR will conduct epidemiological and microbiological investigations in conjunction with affected PHUs. The Ministry of Health will also be involved in the investigation and response and, if the outbreak is likely to be foodborne, the Ministry for Primary Industries will also be involved.

In 2016, there were no multi-regional gastrointestinal outbreaks investigated at the national level. However, a large localised outbreak of Campylobacter associated with a town water supply in Havelock North was investigated by Hawke’s Bay District Health Board (DHB) in collaboration with Hawke’s Bay District Council, Hawke’s Bay Regional Council, ESR, Massey University and the Ministry of Health. A total of 964 cases were officially reported, including 941 from Hawkes Bay DHB and 23 cases from other DHBs. It is estimated that 5500 of Havelock North’s 14,000 residents became ill with campylobacteriosis after consuming contaminated drinking water supplied by two bores on the outskirts of Havelock North [4].


CAUSAL AGENTS

A causal agent was identified in 63.6% (388/610) of outbreaks, involving 76.5% (8436/11,030) of all outbreak-associated cases. In 25 of these outbreaks, two or more causal agents were identified. No specific pathogen or condition was identified in the remaining 222 outbreaks, the vast majority of which were recorded as gastroenteritis (96.8%, 215/222). Acute respiratory infection and influenza-like-illness accounted for the remaining seven outbreaks where no specific pathogen was identified.

As with previous years, enteric agents were implicated in the majority of outbreaks (91.8%, 561/610) and their associated cases (87.6%, 10,378/11,030) (Table 2). Norovirus (30.3%, 185/610) was the most common causal agent implicated in outbreaks in 2016. Norovirus also had the highest proportion of associated cases (50.3%, 5548/11,030) and the highest median number of cases associated with each outbreak (22 cases).

Non-enteric agents accounted for 8.5% (52/610) of outbreaks and 12.8% (1412/11,030) of the outbreak-associated cases in 2016 (Table 2). The most frequently reported non-enteric pathogens and conditions were influenza and influenza-like-illness (3.3% of outbreaks, 20/610). Outbreaks due to influenza and influenza-like-illness also had the highest proportion of associated cases (10.1%, 1119/11,030) and the highest median number of cases associated in each outbreak (20 cases).


Table 2. Outbreaks and associated cases by pathogen, 2016

Pathogen or condition

Outbreaks1 Cases1

Total

% of outbreaks

(n=610)

Median cases per outbreak

Total % of cases (n=11,030)

Enteric 561 91.8 10 10,378 87.6

Norovirus 185 30.3 22 5548 50.3

Giardia spp. 45 7.4 4 238 2.2

Cryptosporidium spp. 33 5.4 4 188 1.7

Sapovirus 24 3.9 23 668 6.1

Salmonella spp.2 24 3.9 3 130 1.2

VTEC/STEC infection 16 2.6 2.5 52 0.5

Campylobacter spp. 15 2.5 3 1008 9.1

Rotavirus 9 1.5 22 223 2.0

Astrovirus 6 1.0 18.5 135 1.2

Yersinia spp. 3 0.5 24 88 0.8

Shigella spp. 2 0.3 6.5 13 0.1

Histamine (scombroid) fish poisoning

2 0.3 2.5 5 0.0

Aeromonas spp. 1 0.2 14 14 0.1

Staphylococcus aureus 1 0.2 14 14 0.1

Clostridium difficile 1 0.2 11 11 0.1

Bacillus cereus 1 0.2 7 7 0.1

Ciguatera fish poisoning 1 0.2 4 4 0.0

Clostridium perfringens 1 0.2 2 2 0.0

Pathogen not identified3 215 35.2 8 2473 22.4

Non-enteric 52 8.5 9.5 1412 12.8

Influenza and influenza-like illness4 20 3.3 20 1119 10.1

Bordetella pertussis 17 2.8 3 108 1.0

Mycobacterium tuberculosis 5 0.8 6 48 0.4

Measles virus 3 0.5 5 98 0.9

Varicella zoster virus 2 0.3 9 18 0.2

Dengue fever 2 0.3 6 12 0.1

Neisseria meningitidis serogroup B 2 0.3 2 4 0.0

Mumps virus 1 0.2 5 5 0.0 1 More than one agent was reported in 25 outbreaks, therefore the numbers don’t add up to the group totals. 2 Includes non-typhoidal Salmonella species only. No outbreaks of Salmonella Typhi or S. Paratyphi were reported in

2016. 3 All enteric outbreaks with no identified pathogen were recorded as gastroenteritis. 4 Includes outbreaks of influenza A (8 outbreaks with 850 cases), influenza B (3 outbreaks, 100 cases), parainfluenza

(2 outbreaks, 48 cases), acute respiratory infection (5 outbreaks, 94 cases) and influenza-like illness (2 outbreaks, 27 cases).


NOROVIRUS OUTBREAKS – GENOTYPES AND OUTBREAK SETTING

Norovirus genotyping is carried out in the Norovirus Reference Laboratory (NRL) at ESR. Phylogenetic analysis is used for genotyping. The Norovirus Typing Tool is used to compare sequences with those in the GenBank database and in the FBVE (Foodborne Viruses in Europe) database [5].

The number of outbreaks reported to the NRL differs from the number recorded in EpiSurv (and therefore reported elsewhere in this report), because not all samples from the norovirus outbreaks reported in EpiSurv are sent to ESR for genotyping and not all gastroenteritis outbreaks caused by norovirus are reported as norovirus in EpiSurv.

In 2016 there were 188 norovirus outbreaks confirmed by the NRL. This is similar to the number of NRL-confirmed outbreaks in 2015 (184 outbreaks) but a decrease from 2014 (312 outbreaks). The highest number of outbreaks occurred in August (31 outbreaks) and the lowest numbers occurred in January and February (6 and 8 outbreaks respectively) (Figure 2).

Figure 2. NRL-confirmed norovirus outbreaks by month and genotype, 2016

The majority (53.2%, 100/188) of norovirus outbreaks confirmed by the NRL occurred in long-term care facilities (including one where an acute-care hospital was identified as a second setting). Outbreaks were also associated with childcare centres (14.9%, 28/188), commercial food operators (8.5%, 16/188), acute-care hospitals (7.4%, 14/188), schools (5.9%, 11/188, including one where a camp was identified as a second setting), and private homes (2.7%, 5/188). Other settings were reported in 12 outbreaks (Figure 3). The setting was unknown in three outbreaks.

0

5

10

15

20

25

30

35

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Nu

mb

er

of

no

rovi

rus

ou

tbre

aks

Month

GI

GII (not genotyped)

Other GII genotypes

GII.4


Figure 3. NRL-confirmed norovirus outbreaks by setting and genotype, 2016

Norovirus genogroup II (GII) was identified in 84.6% (159/188) of outbreaks, and norovirus genogroup I (GI) was identified in 15.4% (29/188) of outbreaks.

The norovirus genotype was determined for 98.9% (186/188) of NRL -confirmed outbreaks. One norovirus GII and one GI were unable to be genotyped. GII.4 was the most common genotype identified and was associated with 45.2% (84/186) of genotyped outbreaks. In 2016, three GII.4 variants were identified. The variant in one GII.4 outbreak was not determined. The GII.4 variants identified were New Orleans_2009/Sydney_2012 (34 outbreaks), Sydney_2012 variant (30 outbreaks) and GII.P16/GII.4 (19 outbreaks). This contrasts to 2014 and 2015 when Sydney_2012 variant was the only GII.4 identified. In total, five GI genotypes and seven GII genotypes (as defined by typing of the viral capsid) were identified. The second most common genotype identified in 2016 was GII.P16/GII.2 (14.5%, 27/186), followed by GII.P12/GII.3 and GII.P17/GII.17 (10.2%, 19/186 each) and GI.3 (8.1%, 15/186). Less commonly identified genotypes included GI.6 (3.2%, 6/186), and GII.7 (6%, 6/186).

Each norovirus outbreak setting was associated with a variety of norovirus genotypes (Figure 3). However, the majority of norovirus outbreaks in acute-care hospitals and long-term care facilities were due to GII.4 (85.7%, 12/14 and 55.0%, 55/100 respectively), compared with a lower proportion (23.0%,17/74) for other settings.

0

20

40

60

80

100

120

Long-termcare facility

Childcarecentre

Commercialfood

operator

Acute-carehospital

School Camp PrivateHome

Other orunknown

Nu

mb

er

of

no

rovi

rus

ou

tbre

aks

Setting

GI

GII (not genotyped)

Other GII genotypes

GII.4


HOSPITALISATIONS AND DEATHS

Hospitalisation information was recorded for 60.2% (367/610) of outbreaks involving 67.9% (7489/11,030) of associated cases. Of these outbreak-associated cases, 3.3% (194/7489) were hospitalised (Table 3). A higher percentage of cases associated with non-enteric outbreaks were hospitalised (23.8%, 67/282 cases) compared with enteric outbreaks (8.0%, 121/1588 cases). The non-enteric pathogen or condition with the highest proportion of hospitalised cases was Neisseria meningitidis serogroup B (100.0%, 2/2 cases), followed by dengue fever (50.0%, 6/12 cases). Of the enteric pathogens and conditions ciguatera fish poisoning (100.0%, 4/4 cases) represented the highest proportion of hospitalised cases, followed by Salmonella spp. (83.3%, 15/18 cases).

Ten deaths were associated with eight different outbreaks in 2016. The deaths were associated with Campylobacter spp. (3 deaths), norovirus (2), VTEC/STEC infection (1), influenza A (1) and parainfluenza (1). A pathogen was not identified in three deaths (gastroenteritis (2), acute respiratory infection (1)). Note both norovirus and influenza A were identified in one outbreak involving one death.


Table 3. Hospitalised outbreak cases and total outbreak cases by pathogen or condition, 2016


Outbreaks1 Cases1

Total Total No. of cases hospitalised2

% of cases hospitalised

Enteric 35 1588 127 8.0

Campylobacter spp. 2 971 41 4.2

Norovirus 13 409 29 7.1

Sapovirus 2 40 22 55.0

Salmonella spp.3 4 18 15 83.3

VTEC/STEC infection 3 9 6 66.7

Ciguatera fish poisoning 1 4 4 100.0

Rotavirus 2 56 2 3.6

Giardia spp. 2 11 2 18.2

Yersinia enterocolitica 1 24 1 4.2

Astrovirus 1 14 1 7.1

Cryptosporidium spp. 1 2 1 50.0

Pathogen not identified4 4 37 4 10.8

Non-enteric 18 282 67 23.8

Measles virus 2 94 27 28.7

Influenza and influenza-like-illness5 5 119 20 16.8

Mycobacterium tuberculosis 4 44 8 18.2

Dengue fever 2 12 6 50.0

Bordetella pertussis 4 11 4 36.4

Neisseria meningitidis serogroup B 1 2 2 100.0

Total 53 1870 194 10.4 1 More than one enteric agent was reported in 25 outbreaks, therefore the numbers don’t add up to the group totals. 2 Hospitalisation information was recorded for 60.2% (367/610) of outbreaks, relating to 67.9% (7489/11,030) of

cases. Only outbreaks where one or more hospitalisations were recorded were included in the table (53 outbreaks involving 1870 cases).

3 Includes non-typhoidal Salmonella species only. No outbreaks of Salmonella Typhi or Salmonella Paratyphi were reported in 2016.

4 All enteric outbreaks with no identified pathogen were recorded as gastroenteritis. 5 Includes outbreaks of influenza A (6 outbreaks with 813 cases), influenza B (2 outbreaks, 70 cases), acute

respiratory infection (2 outbreaks, 57 cases) and influenza-like illness (1 outbreak, 14 cases).


OUTBREAK SETTINGS

The most common outbreak setting recorded was long-term care facilities (33.3%, 203/610) followed by childcare centres (18.0%, 110/610) and private homes (16.4%, 100/610). Outbreaks in long-term care facilities had the highest number of associated cases (39.8%, 4393/11,030) (Table 4). Overall, 65.1% (397/610) of all outbreaks and 78.3% (8636/11,030) of cases reported in 2016 were set in institutions. The setting was unknown in 3.1% (19/610) of outbreaks.

Table 4. Outbreaks and associated cases by setting of exposure/transmission, 2016

Outbreak setting

Outbreaks1 Cases1

Total % of

outbreaks (n=610)

Total % of cases (n=11,030)

Institutions 397 65.1 8636 78.3

Long-term care facility 203 33.3 4393 39.8

Childcare centre 110 18.0 2095 19.0

School 29 4.8 1363 12.4

Hospital (acute-care) 29 4.8 370 3.4

Camp 8 1.3 188 1.7

Hotel/motel 4 0.7 77 0.7

Hostel/boarding house 3 0.5 30 0.3

Other institution 15 2.5 199 1.8

Commercial food operators 70 11.5 474 4.3

Restaurant/café/bakery 46 7.5 317 2.9

Takeaway 11 1.8 48 0.4

Supermarket/delicatessen 3 0.5 7 0.1

Caterer 1 0.2 10 0.1

Fast food restaurant 1 0.2 7 0.1

Other food outlet 9 1.5 88 0.8

Workplace 9 1.5 35 0.3

Farm 5 0.8 15 0.1


Other 128 21.0 1728 15.7

Private home 100 16.4 411 3.7

Other setting 22 3.6 228 2.1

Community/church or sports gathering 8 1.3 1102 10.0

Aeroplane 1 0.2 5 0.0

Unknown setting 19 3.1 267 2.4 1 More than one setting was recorded in 21 outbreaks, therefore the numbers don’t add up to the group totals.


MODES OF TRANSMISSION

In 2016, the most commonly reported mode of transmission was person-to-person (82.3%, 502/610 outbreaks), followed by foodborne (15.6% 95/610) and environmental (11.1%, 68/610) (Table 5). Person-to-person transmission also accounted for the highest percentage of associated cases (85.0%, 9376/11,030), followed by environmental transmission (16.7%, 1842/11,030). The mode of transmission was unknown for 4.1% (25 outbreaks).

Table 5. Outbreaks and associated cases by mode of transmission, 2016

Mode of transmission

Outbreaks Cases

Primary mode

Secondary mode

Total % of

outbreaks (n=610)1

Total % of cases (n=11,030)1

Person-to-person 414 88 502 82.3 9376 85.0

Foodborne 78 17 95 15.6 1139 10.3

Environmental 13 55 68 11.1 1842 16.7

Waterborne 10 4 14 2.3 1007 9.0

Zoonotic 8 5 13 2.1 47 0.4

Vectorborne 2 0 2 0.3 12 0.1

Other 2 0 2 0.3 5 0.0

Unknown - - 25 4.1 111 1.0 1 More than one mode of transmission was recorded for 98 outbreaks therefore the totals add up to more than 100%.

Note: No outbreaks with sexual contact or parenteral transmission were reported in 2016.

In 2016, a higher proportion of cases (9.0%) were associated with waterborne outbreaks than in previous years (2015: 1.0%, 2014: 0.9%, 2013: 3.2%). This was primarily due to a large Campylobacter outbreak (involving 964 cases) linked to drinking water in Havelock North.


FOODBORNE OUTBREAKS

Causal agent

Of the 95 foodborne outbreaks reported in 2016 (with 1139 associated cases), 54.7% (52/95 outbreaks) were linked to a pathogen or condition (Table 6). Pathogens most commonly associated with foodborne outbreaks were norovirus (18.9%, 18/95 outbreaks) and Salmonella spp. (12.6%, 12/95 outbreaks). Enteric bacteria (Campylobacter spp., Salmonella spp., Yersinia spp., Shigella spp., VTEC/STEC, S. aureus, B. cereus and C. perfringens) were implicated in 28.4% (27/95) of the foodborne outbreaks. Enteric viruses (norovirus and sapovirus) were implicated in 20.0% (19/95) of the foodborne outbreaks.

Table 6. Foodborne outbreaks and associated cases by pathogen or condition, 2016


Outbreaks Cases

Total % of outbreaks

(n=95)1 Total

% of cases (n=1139)1

Norovirus 18 18.9 542 47.6

Salmonella spp. 12 12.6 78 6.8

Campylobacter spp. 8 8.4 28 2.5

Giardia spp. 4 4.2 18 1.6

Yersinia spp. 2 2.1 75 6.6

Histamine (scombroid) fish poisoning

2 2.1 5 0.4

Sapovirus 1 1.1 65 5.7

Staphylococcus aureus 1 1.1 14 1.2

VTEC/STEC infection 1 1.1 11 1.0

Shigella spp. 1 1.1 8 0.7

Bacillus cereus 1 1.1 7 0.6

Ciguatera fish poisoning 1 1.1 4 0.4

Clostridium perfringens 1 1.1 2 0.2

Cryptosporidium spp. 1 1.1 2 0.2

Pathogen not identified2 43 45.3 292 25.6 1 More than one agent was reported in two foodborne outbreaks, therefore the totals add up to more than 100%. 2 All enteric outbreaks with no identified pathogen were recorded as gastroenteritis.


Setting where contaminated foods/beverages were prepared

The setting where foods and beverages were prepared was recorded in 83.2% (79/95) of foodborne outbreaks and 70.1% (799/1139) of associated cases in 2016. The preparation settings most commonly associated with foodborne outbreaks included commercial food operators (60.0%, 57/95) and private homes (9.5%, 9/95) (Table 7). Foodborne outbreaks where the food was prepared in restaurants, cafés, or bakeries had the highest number of associated cases (20.4%, 232/1139).

Table 7. Foodborne outbreaks and associated cases by setting of food preparation, 2016

Preparation setting

Outbreaks Cases1

Total % of outbreaks

(n=95) Total

% of cases (n=1139)

Commercial food operators 57 60.0 329 28.9

Restaurant/café/bakery 35 36.8 232 20.4

Takeaway 12 12.6 52 4.6

Supermarket/delicatessen 3 3.2 7 0.6

Fast food restaurant 1 1.1 7 0.6

Other food outlet 7 7.4 34 3.0

Institutions 8 8.4 260 22.8

Long-term care facility 2 2.1 38 3.3

Hotel/motel 2 2.1 67 5.9

School 1 1.1 68 6.0

Childcare centre 1 1.1 54 4.7

Camp 1 1.1 24 2.1

Hostel/boarding house 1 1.1 9 0.8

Other 16 16.8 214 18.8

Private home 9 9.5 45 4.0

Community/church gathering 2 2.1 62 5.4


Farm 1 1.1 2 0.2

Overseas manufacturer 1 1.1 2 0.2

Other setting 2 2.1 98 8.6

Unknown preparation setting 16 16.8 340 29.9 1 Two preparation settings were recorded in three foodborne outbreaks, therefore the numbers don’t add up to

the group totals.

Additional information on foodborne outbreaks can be found in the Foodborne disease in New Zealand 2016 report [6].


PERSON-TO-PERSON OUTBREAKS

Causal agents

In 2016, there were 502 person-to-person outbreaks (primary and secondary mode of transmission) with 9376 associated cases. A causal agent was identified in 66.7% (335/502) of these outbreaks. The most common causal agent was norovirus, which was recorded in 34.9% (175/502) of person-to-person outbreaks and involved 57.7% (5412/9376) of outbreak-associated cases (Table 8). Other common pathogens and conditions included Giardia spp. (6.6%, 33/502) and sapovirus (4.8%, 24/502). Influenza or influenza-like illness accounted for 20 (4.0%) outbreaks and had a high number of associated cases (11.9%, 1119/9376).

Table 8. Person-to-person outbreaks and associated cases by pathogen or condition, 2016


Outbreaks1 Cases

Primary mode

Secondary mode

Total % of

outbreaks (n=502)2

Total % of

cases (n=9376)2

Norovirus 145 30 175 34.9 5412 57.7

Giardia spp. 28 5 33 6.6 178 1.9

Sapovirus 21 3 24 4.8 668 7.1

Cryptosporidium spp. 17 4 21 4.2 132 1.4

Influenza and influenza-like-illness3

19 1 20 4.0 1119 11.9

Bordetella pertussis 16 1 17 3.4 108 1.2

Salmonella spp.4 10 5 15 3.0 91 1.0

VTEC/STEC infection 9 5 14 2.8 37 0.4

Rotavirus 7 2 9 1.8 223 2.4

Astrovirus 5 1 6 1.2 135 1.4

Mycobacterium tuberculosis 5 0 5 1.0 48 0.5

Campylobacter spp. 3 2 5 1.0 14 0.1

Measles virus 3 0 3 0.6 98 1.0

Varicella zoster virus 2 0 2 0.4 18 0.2

Neisseria meningitidis serogroup B

1 1 2 0.4 4 <0.1

Aeromonas spp. 0 1 1 0.2 14 0.1

Yersinia spp. 1 0 1 0.2 13 0.1

Clostridium difficile 1 0 1 0.2 11 0.1

Shigella spp. 1 0 1 0.2 5 0.1

Mumps virus 1 0 1 0.2 5 0.1

Pathogen not identified5 138 29 167 33.3 2206 23.5 1 Includes outbreaks where person-to-person transmission was either the primary or secondary mode of transmission reported. 2 Multiple agents were reported in 20 person-to-person outbreaks, therefore the totals add up to more than 100%. 3 Includes non-typhoidal Salmonella species only. No outbreaks of Salmonella Typhi or S. Paratyphi were reported in 2016. 4 Includes outbreaks of influenza A (8 outbreaks with 850 cases), influenza B (3 outbreaks, 100 cases), parainfluenza (2 outbreaks,

48 cases), acute respiratory infection (5 outbreaks, 94 cases) and influenza-like illness (2 outbreaks, 27 cases). 5 All enteric outbreaks with no identified pathogen were recorded as gastroenteritis.


WATERBORNE OUTBREAKS

Causal agents

There were 14 waterborne outbreaks with 1007 associated cases in 2016. A causal agent was identified in most (92.9%, 13/14) of the outbreaks (Table 9). The most commonly reported waterborne pathogens and conditions were Giardia spp. (35.7%, 5/14 outbreaks), Cryptosporidium spp. and VTEC/STEC infection (21.4%, 3/14 outbreaks each). In 2016 the largest proportion of cases linked to waterborne outbreaks was due to Campylobacter spp. This was due to a large outbreak involving 964 notified cases associated with a contaminated drinking water supply in Havelock North during August 2016. This was the largest waterborne outbreak recorded in New Zealand since recording began in EpiSurv in 1997.

Table 9. Waterborne outbreaks and associated cases by pathogen, 2016


Outbreaks1 Cases

Primary mode

Secondary mode

Total % of

outbreaks (n=14)

Total % of

cases (n=1007)

Giardia spp. 4 1 5 35.7 16 1.6

Cryptosporidium spp. 3 - 3 21.4 9 0.9



Pathogen not identified2 - 1 1 7.1 6 0.6 1 Includes outbreaks where waterborne transmission was either the primary or secondary mode of transmission

reported. 2 All enteric outbreaks with no identified pathogen were recorded as gastroenteritis.


ENVIRONMENTAL OUTBREAKS

Causal agents

There were 68 environmental outbreaks with 1842 associated cases reported in 2016. Of these outbreaks, 73.5% (50/68) were linked to a specific causal agent (Table 10). The most common causal agent identified in environmental outbreaks was norovirus (38.2%, 26/68), followed by Giardia spp. (14.7%, 10/68). Environmental transmission was the secondary mode reported in all of the norovirus outbreaks. Norovirus also accounted for the highest proportion of associated cases (70.0%, 1350/1842) followed by influenza A (38.2%, 737/1842).

Table 10. Environmental outbreaks and associated cases by pathogen or condition, 2016


Outbreaks1 Cases

Primary mode

Secondary mode

Total % of

outbreaks (n=68)2

Total % of cases (n=1842)2

Norovirus 0 26 26 38.2 1350 70.0

Giardia spp. 6 4 10 14.7 56 2.9




Influenza A 0 2 2 2.9 737 38.2

Sapovirus 0 2 2 2.9 48 2.5

Rotavirus 0 2 2 2.9 29 1.5

Salmonella spp. 2 0 2 2.9 5 0.3

Astrovirus 0 1 1 1.5 14 0.7

Pathogen not identified3

2 16 18 26.5 315 16.3

1 Includes outbreaks where environmental transmission was either the primary or secondary mode of transmission reported. 2 Two pathogens were reported in six environmental outbreaks, therefore the totals add up to more than 100%. 3 All enteric outbreaks with no identified pathogen were recorded as gastroenteritis.


ZOONOTIC OUTBREAKS

Causal agents

There were 13 zoonotic outbreaks, with 47 associated cases in 2016. All were linked to a specific pathogen (Table 11). Cryptosporidium spp. was the most commonly identified pathogen and was linked to 30.8% (4/13) of zoonotic outbreaks and 44.7% (21/47) of the associated cases.

Table 11. Zoonotic outbreaks and associated cases by pathogen or condition, 2016


Outbreaks1 Cases

Primary mode

Secondary mode

Total % of

outbreaks (n=13)

Total % of

cases (n=47)


Giardia spp. 1 2 3 23.1 11 23.4


VTEC/STEC infection 2 1 3 23.1 7 14.9 1 Includes outbreaks where zoonotic transmission was either the primary or secondary mode of transmission reported.


TIME TRENDS 2006–2016

Between 2006 and 2014, both the number of outbreaks per 100,000 population and the number of cases per 100,000 increased overall, although there was a lot of variability during that time period. The outbreak rate peaked in 2014 (19.1 outbreaks per 100,000 population) and then decreased significantly (p<0.05) in 2015 to 12.2 outbreaks per 100,000. The rate in 2016 (13.0 outbreaks per 100,000) was similar to that reported in 2015 (Figure 4). Similarly, the number of cases per 100,000 peaked in 2014 with 328.7 of cases per 100,000 and then decreased to 185.3 per 100,000 in 2015. However, the rate increased significantly in 2016 to 235.1 per 100,000 population, which is largely due to the Havelock North campylobacteriosis outbreak (involving 964 cases) reported in August 2016.

Figure 4. Outbreaks and associated cases per 100,000 by year, 2006–2016

From 2006 to 2015, the proportion of outbreaks linked to an identified causal agent was around 75% (range 68.7–79.3%). In 2016, this proportion was lower at 64.8% (395/610). The causal agent associated with the highest number of outbreaks and outbreak cases during 2006–2015 was norovirus, although the number and percentage varied considerably from year to year. In 2016, 185 norovirus outbreaks were reported with 5548 associated cases. This figure is much lower than the number of norovirus outbreaks reported in 2014 (326 outbreaks and 9390 cases), when the highest number of norovirus outbreaks and cases were recorded since reporting began in EpiSurv in 1997. Since 2006, norovirus outbreaks have accounted for around a third of outbreaks reported each year, with the exception of 2009 when the proportion was 45.4% (290/639 outbreaks) (Figure 5).

0

50

100

150

200

250

300

350

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15

20

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2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016

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Figure 5. Percentage of outbreaks by pathogen or condition and year, 2006–2016

The number of reported rotavirus outbreaks has progressively increased, from six in 2006 (78 cases) to 47 in 2014 (854 cases). In 2015, there was a significant decrease in the number of rotavirus outbreaks (three outbreaks including two where norovirus was also identified) and associated cases (57 cases) reported. This decrease is most likely associated with the introduction of rotavirus vaccine to the infant immunisation schedule in July 2014 [7]. In 2016, there were nine rotavirus outbreaks (with 223 associated cases) including two outbreaks where influenza A was also identified and one outbreak where norovirus was also identified. Five outbreaks were in childcare centres in the Wellington region, and the remaining four outbreaks were in long-term care facilities.

There was a decrease in the number of outbreaks due to VTEC/STEC infection in 2016 (16 outbreaks, 52 cases) compared to 2015 (17 outbreaks, 94 cases). However, the number of outbreaks and associated cases reported annually since 2012 has increased significantly. Between 2006 and 2012 there was an average of four outbreaks and 16 associated cases reported each year. The most common mode of transmission (primary and secondary) reported for VTEC/STEC outbreaks in 2016 was person-to-person (14 outbreaks, 37 cases). The introduction of more sensitive testing methods in diagnostic laboratories since mid-2015 may have contributed to the increased detection of outbreaks of some enteric diseases.

The number of outbreaks and cases due to Cryptosporidium spp. increased in 2016 (33 outbreaks, 188 cases) compared with 2015 (21 outbreaks, 94 cases). However, the number of outbreaks and cases were significantly lower than reported in 2013 (99 outbreaks, 550 cases) when outbreaks of Cryptosporidium spp. peaked. The most common mode of transmission (primary and secondary) reported for Cryptosporidium spp. outbreaks in 2016 was person-to-person (21 outbreaks, 132 cases).

The number of outbreaks due to Giardia spp. increased from 2007 (22 outbreaks, 117 cases) and peaked in 2010 (97 outbreaks, 378 cases). In 2016, there were 45 outbreaks with 238 associated cases, similar to 2015 (45 outbreaks, 207 cases) and significantly lower than the number of outbreaks reported between 2010 and 2014 (range 70–97). The most

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016

Per

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utb

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Year

Norovirus Giardia CampylobacterSalmonella Cryptosporidium VTEC/STECOther Unidentified pathogen


common mode of transmission (primary and secondary) reported for Giardia spp. outbreaks in 2016 was person-to-person (33 outbreaks, 178 cases).

There was a large reduction in the number of outbreaks and associated cases of Campylobacter spp. reported in 2007, when numbers reduced by more than half from 2006 (47 outbreaks, 221 cases) to 2007 (21 outbreaks, 60 cases). This decrease was most likely due to interventions put in place in New Zealand in 2006 to reduce the incidence of poultry-associated foodborne campylobacteriosis [8]. The number of outbreaks and associated cases of Campylobacter spp. increased steadily between 2009 (13 outbreaks, 69 cases) and 2014 (35 outbreaks, 241 cases). In 2016, the number of outbreaks reported (15 outbreaks) was the lowest since 2009, while the number of associated cases was the largest since recording began (1008 cases). The Havelock North waterborne outbreak in August 2016 accounted for 964 notified cases. There were 44 cases associated with the remaining 14 outbreaks reported in 2016. More than half (57.1%, 8/14) were due to foodborne transmission; raw milk was implicated in three of the outbreaks involving 16 cases and chicken liver pate was implicated in three outbreaks involving seven cases. A source was not identified in the other two foodborne outbreaks.

Outbreaks of other pathogens and conditions that have emerged in recent years include varicella zoster virus (chicken pox) (2014: 2 outbreaks, 45 cases; 2015: 1 outbreak, 22 cases, 2016: 2 outbreaks, 18 cases) and respiratory syncytial virus (RSV) (2015: 1 outbreak, 33 cases). In 2016 there were two outbreaks of dengue fever involving 12 cases. Both outbreaks involved travel groups to Bali, Indonesia, where the infection was acquired. Prior to these, the last dengue fever outbreaks were reported in 2010 (2 outbreaks, 4 cases).

In 2016, there were three outbreaks of measles involving 98 cases reported. This was higher than reported in 2015 (2 outbreaks, 6 cases) and also the fourth highest number of outbreak cases for measles since recording began in EpiSurv in 1997. The years with the largest number of measles outbreak cases were 2011 (6 outbreaks, 582 cases), 2014 (19 outbreaks, 243 cases) and 2009 (3 outbreaks, 205 cases). Waikato DHB reported the largest outbreak in 2016 involving 89 cases across five DHBs.

The most common outbreak settings in 2016 were long-term care facilities, childcare centres and private homes. Approximately one fifth (18.0%, 100 outbreaks) of outbreaks were set in childcare centres, which is the highest proportion since recording began (range 2.4–15.5%). Since 2006, outbreaks in institutions have accounted for one-half to two-thirds of all outbreaks reported annually, and those in private homes for around one-fifth to one-third. Before 2006, commercial food operators and private homes were the most commonly reported settings.

Outbreaks involving person-to-person transmission have been the most frequently reported mode of transmission since 2006. This was a change from foodborne transmission, which was the most frequent mode between 1998 and 2006 (range 28.3–52.9%). Between 2007 and 2016, the proportion of foodborne outbreaks reported each year ranged from 13.2 to 23.3% (2016: 15.6%, 95 outbreaks). In 2016, the number of outbreaks with person-to-person transmission (82.3%, 502/610) was more than four times higher than any other mode of transmission, similar to the previous five years. Foodborne transmission (15.6%, 95/610) was the second most common mode of transmission in 2016. In outbreaks reported from 2013 to 2015 environmental transmission was the second most common mode of transmission reported.



GLOSSARY

Common event outbreak

An outbreak due to the exposure of a group of persons to a noxious influence that is common to the individuals in the group, where the exposure is brief and essentially simultaneous and all resultant cases develop within one incubation period of the disease. Cases therefore have exposures that are grouped in place and time (synonymous with point source outbreak).

Common site outbreak

An outbreak due to the exposure of a group of persons to a noxious influence that is common to the individuals in the group, where exposures have occurred at the same place (or site) but over a longer time period than those of common event outbreaks (ie, grouped in place but not in time).

Common source outbreak

An outbreak due to the exposure of a group of persons in the community to a noxious influence that is common to the individuals in the group. These outbreaks are subcategorised into common event (where exposures are grouped in time and place), dispersed common source (grouped in time but not in place) and common site (grouped in place but not in time).

Community-wide outbreak

An outbreak among individuals in a community where transmission is predominantly by direct exposure of susceptible people to infectious people (synonymous with person-to-person outbreak).

Contamination

The presence of a disease-causing agent on a body surface, in clothes, bedding, toys or other inanimate articles, or substances such as water and food.

Dispersed common source outbreak

Outbreak due to the exposure of a group of persons in the community to a noxious influence that is common to the individuals in the group, where the exposures are not grouped in place (and may or may not be grouped in time). These outbreaks are often due to a distributed vehicle of infection transmission, such as a commercially prepared food item or a water supply.

Environment

All factors that are external to the individual human host.


EpiSurv

The national notifiable disease surveillance system that ESR manages to record data about notifiable diseases and outbreaks reported by public health units.

Exposure

Proximity and/or contact with a potential source of a disease agent in such a manner that effective transmission of the agent and harmful or protective effects of the agent may occur.

Household outbreak

An outbreak confined to members of a single household.

Institutional outbreak

An outbreak confined to the population of a specific residential or other institutional setting, such as a hospital, long-term care facility, prison, childcare centre or school.

Outbreak

Two or more cases of a specific disease or health-related condition linked to a common source, in particular, where the common source is exposure at a common event, or food or water dispersed in a community, an environmental source or a source in an institutional setting; OR a community-wide or person-to-person outbreak; OR any other situation where the outbreak investigation or control measures are being used or considered.

Source (of illness)

The person, animal, object or substance from which a disease agent passes to a host.

Transmission of illness

Any mechanism by which a disease agent is spread through the environment or to another person. Mechanisms are defined as either direct or indirect.

Vehicle

An inanimate intermediate in the indirect transmission of a pathogen from a reservoir or infected host to a susceptible host; vehicles include foods, clothing and instruments.


REFERENCES

1. Ministry of Health. 2009. Guidelines for the Management of Norovirus Outbreaks in Hospitals and Elderly Care Institutions. Wellington. https://www.health.govt.nz/system/files/documents/publications/guidelines-management-norovirus_0.pdf

2. ESR. 2012. Guidelines for the Investigation and Control of Disease Outbreaks. Porirua, New Zealand: Institute of Environmental Science & Research Limited. https://surv.esr.cri.nz/episurv/Manuals/GuidelinesForInvestigatingCommDiseaseOBs.pdf

3. ESR. 2017. Notifiable Diseases in New Zealand Annual Report 2016. Porirua, New Zealand: Institute of Environmental Science and Research Limited. https://surv.esr.cri.nz/PDF_surveillance/AnnualRpt/AnnualSurv/2016/2016AnnualNDReportFinal.pdf

4. Government Inquiry into Havelock North Drinking Water. 2017. Report of the Havelock North Drinking Water Inquiry. Auckland, New Zealand. https://www.dia.govt.nz/Government-Inquiry-into-Havelock-North-Drinking-Water

5. Kroneman A, Vennema H, Deforche K, et al. 2011. An automated genotyping tool for enteroviruses and noroviruses. J Clin Virol 51(2): 121-5.

6. Pattis I, Lopez L, Cressey P, et al. 2017. Annual Report Concerning Foodborne Disease in New Zealand 2016. Christchurch, New Zealand: Institute of Environmental Science and Research Ltd. http://www.mpi.govt.nz/dmsdocument/19700

7. Ministry of Health. 2014. Immunisation Handbook 2014. Wellington: Ministry of Health. http://www.moh.govt.nz/notebook/nbbooks.nsf/0/5B75258BCFDED7CACC257CF4007CE5B8/$file/immunisation-handbook-may14-v2.pdf

8. Sears A, Baker M, Wilson N, et al. 2011. Marked Campylobacteriosis Decline after Interventions Aimed at Poultry, New Zealand. Emerg Infect Dis 17(6): 1007-15.



APPENDIX

OUTBREAK REPORT FORM








Documents

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